Blue-green algae have been in the news recently. Blooms of the algae have led the North Dakota Department of Health to issue public health warnings for several lakes across the state.
There are several types of algae that are common in our marshes, lakes, rivers, and streams. They are important to the food chains in these bodies of water, and serve as little aerators, by releasing oxygen into the water as a byproduct of photosynthesis. Most of the time we don’t even notice them, but if conditions are right, their populations may erupt, causing an algae bloom. These blooms may be unsightly and perhaps a nuisance, but with the exception of blue-green algae, generally do not pose a health risk.
The term algae is a generic term that generally refers to microscopic photosynthesizing organisms that live in the water. The types of algae (e.g. green algae, red algae, blue-green algae) may not be closely related in terms of how they are classified or their toxicity. However, some groups such as the blue-green algae are well known for their toxins.
Blue-green algae are common residents of freshwater habitats. They are close relatives of bacteria and are now more accurately called cyanobacteria. Most species do not pose a health problem, but some are known to produce strong toxins that can damage the liver and/or nerve cells.
Identifying the algal species of a bloom is difficult. However, blooms of blue-green algae are often described as looking like pea soup on the water surface or spilled green paint. Any animal drinking from these waters is at risk. Some of you may recall instances where livestock, horses, or dogs have died from drinking water in the area of one of these blooms. Wading or swimming in one of these bodies of water may even pose health risks for humans, for example gastroenteritis, skin rashes and breathing problems.
So why do these blooms occur? Warm water temperatures, such as we might expect this time of year are conducive to these algae blooms. Nutrient enrichment is also a factor, such as that from fertilizer runoff, or enrichment from animal waste.